Solution processing of hybrid ZnO nanophosphors assembled in mesosphere for LED application
Résumé
An important economic improvement of white light emitting diode (LED) is based on the use of lanthanide-free phosphors that are supposed to convert UV light into visible one, thanks to down-conversion (DS) process. ZnO nanoparticles have aroused an increasing interest since they possess a variety of intrinsic defects that provide light emission in the visible range without the introduction of any additional impurity. Our recent patented industry-capable (in terms of legislation concerns) and cost effective chemical solution approach (PCT WO 2016/038317 A1) led to mesospheric self-assembly hybrid ZnO-PAA nanomaterials (PAA = polyacrylic acid) that can be used as original nanostructured material which revealed to be efficient scatterer, resulting in a significant increase of the light-harvesting capability and emission performance. Herein, we will address the use of such self-assembly nanostructured ZnO materials as luminophor for LED devices. We will demonstrate how and why optimizations of (i) the set-up of the synthesis (reaction and washing steps), (ii) the molecular weight of the commercial polymers PAAH and PAANa (1800-250000) and the ratio of their mixture, (iii) cationic doping and (iv) core-shell structure lead to remarkable efficiency of white emission light of DS thin films in LED technology